This invention relates to serial printers and, more particularly, to control apparatus for serial printers.
Serial printers have taken many forms over the decades with the most common and widespread one being the typewriter. In recent years, the seemingly exponentially increasing use of computer-based high speed information processing systems has placed a strong demand on serial printers in terms of speed, performance and reliability. Prior art serial printers especially adapted to print computerbased output data have, in the past, relied upon hard-wired control logic to implement the many control functions and operations required. An example of one such printer is disclosed in U.S. application Ser. No. 505,105 filed in the name of Andrew Gabor on Sept. 11, 1974 for HIGH SPEED PRINTER WITH INTERMITTENT PRINT WHEEL AND CARRIAGE MOVEMENT and assigned to the assignee of the present invention.
Copending U.S. application Ser. No. 682,877 referred to above is directed to the employment of a programmed data processor as a control apparatus for a serial printer in order to improve the speed, performance and reliability of serial printers over prior art hardwired systems. In any programmed data processor type of controller, an interface must be employed to receive incoming data and assemble it into a format utilizable by the particular processor employed. This incoming data may be and is usually random, i.e. asynchronous, relative to the synchronous operation of the processor.
It would be desirable, therefore, to include in the interface logic a means for informing the processor of the order in which various motion commands are received by the printer so that the processor can operate the printer accordingly. In terms of printer disclosed in the aforementioned U.S. application Ser. No. 505,105, received motion commands may be representative of new desired positions for a rotatable print member, linearly movable carriage and paper feed apparatus.